I would reccomend ASCA. I plan to do Rally and OB(and agility) through ASCA with the new pup and Abby. PM me and I can give you the link to a couple training places that hold trials. I've gone to some trials and it's an extremely relaxed enviorment(at least the ones I've gone to) not to mention completely filled with Aussies!!!

OP - APDT Rally is in the process of being sold, so it's probably best not to do it until all the things about titles, ribbons, and new owners are sorted out. Grandfathering of titles isn't guaranteed, so..